The Supreme Court justices voted 8 to 1 that Florida’s system of imposing the death penalty is unconstitutional. Florida legislators said they will change state law to meet the court’s specifications. (Joshua Roberts/Reuters)

The Supreme Court found Florida’s unique system of imposing a death sentence unconstitutional on Tuesday, saying it gives power to judges that is rightfully reserved for juries.

The decision united the court’s liberals and most of its conservatives, who voted 8 to 1 against the system employed by a state that’s among the leaders in imposing capital punishment. Florida has nearly 400 inmates on death row.

Justice Sonia Sotomayor said Florida’s process reduces the jury’s role to an advisory one and leaves the work of finding the special circumstances that render a murderer eligible for the death penalty up to a judge.

That is the reverse of what the court in 2002 said was required, she wrote.

The Constitution means for “a jury, not a judge, to find each fact necessary to impose a sentence of death,” Sotomayor wrote. “A jury’s mere recommendation is not enough.”

It seems likely that the ruling will have limited impact outside of Florida, because no other state has exactly the same procedure. Alabama, another state with a higher-than-average history of imposing the death penalty, allows a judge to overrule a jury’s findings about whether the convicted person should be put to death.

Sotomayor acknowledged that the Supreme Court had twice upheld Florida’s death penalty process. But the court’s ruling Tuesday overturned those decisions and said they did not square with the court’s more recent rulings.

In a 2002 decision in an Arizona death penalty case, the court said the constitutional right to a “speedy and public trial, by an impartial jury” meant that a jury must find the facts necessary to sentence a defendant to death.

The Florida case was brought by Timothy Lee Hurst, who was convicted of the 1998 murder of Cynthia Lee Harrison, his co-worker at a Popeyes fast-food restaurant in Pensacola.

As in other places, Florida requires a jury in the sentencing phase of a trial to consider aggravating circumstances that would make a defendant eligible for the death penalty — in Hurst’s case, that the crime was committed during a robbery, and that it was particularly “heinous, atrocious or cruel” — along with mitigating circumstances, such as a defendant’s low IQ or childhood abuse.

But the state does not require the jury to be unanimous in recommending death. In Hurst’s case, the jury recommended death on a vote of 7 to 5, citing the two aggravating circumstances. But it is unclear whether all seven agreed on both, or, for instance, whether four agreed on one and three on the other.

The Florida jury was also told that its recommendation was not binding and that it was up to the judge to make a final decision. And the judge could consider evidence that the jury did not.

The decision to sentence Hurst to death must be based “on a jury’s verdict, not a judge’s fact-finding,” Sotomayor wrote. “Florida’s sentencing scheme, which required the judge alone to find the existence of an aggravating circumstance, is therefore unconstitutional.”

Conservative justices Antonin Scalia and Clarence Thomas were part of the court’s 2002 decision about Arizona’s sentencing system.

In his dissent, Alito questioned the ruling and said Florida’s system gave the jury enough of a role.

“The trial court performs what amounts, in practical terms, to a reviewing function,” wrote Alito, who has emerged as the justice least sympathetic to criminal defendants.

He said it “defies belief” that the jury would not have found the murder of Harrison heinous. He said her stabbing death probably took 15 minutes and noted that the judge wrote that “the utter terror and pain that Ms. Harrison likely experienced during the incident is unfathomable.”

The court’s decision returns Hurst’s case to lower courts. It is unclear what effect it will have on other death row inmates. Generally, the court’s rulings are prospective rather than guaranteeing new sentencing for those already convicted.

Leaders of the Florida legislature, who gathered in Tallahassee for their annual session, said they will quickly change state law to meet the high court’s specifications.

Robert Barnes has been a Washington Post reporter and editor since 1987. He joined The Post to cover Maryland politics, and he has served in various editing positions, including metropolitan editor and national political editor. He has covered the Supreme Court since November 2006.